Holiday

I've just come home from a family holiday in South Devon. We stayed in an Airbnb and hired a little sailing boat. The boat was a joy and the house was like a brilliant scavenger hunt. If you looked hard enough you could find almost anything you wanted. Crabbing equipment, camping stove, parasol, tablecloth, spare light bulbs, weighing scales, board games... There were 2 exceptions. We never found the salt and pepper (although we all think that it was in there somewhere and we just hadn't located it) and there were no towels.

The main theme of the holiday was not being dry, despite staying over mid-summer's day during a heatwave. The house is built into the shady side of a hill beside a creek, it doesn't have good ventilation and everything associated with it is slightly damp. We all thought we might catch mildew or mould when we went to sleep. After going and buying a towel my sister-in-law had a bath and the bathroom ended up so steamy and covered in condensation that she was actually unable to get herself dry afterwards.

Some of the roving on our little boat had gone loose and water was constantly weeping inwards – to the extent that the owner had fitted an automatic electric bilge pump and a big battery to keep the thing afloat when it was on the mooring. It worked perfectly and fitted in nicely with the theme of our holiday.

Richard "Poacher's Pocket" B

Book Review

Ignition!

I have just read "Ignition!" by John D. Clark. It's an informal history of liquid rocket propellants and while it's a great read I'd have probably enjoyed it more if I had a degree in chemistry. Some great authors send multiple characters (or generations of characters) through similar trials, or have recurring themes that affect all the characters. (I'm looking at you Hugo, Dumas, Tolstoy, etc.) In Clarke's book  you get something similar, but the characters are hard to relate to and have difficult names like C-stoff, S-stoff, N2O4, Mixed Oxides of Nitrogen, Inhibited Red Fuming Nitric Acid and Unsymmetrical Dimethyl Hydrazine. The recurring themes are eutectics, equilibrium mixtures, toxicity, corrosion, unacceptable freezing points and the tendency to explode unexpectedly.

Asimov writes a gushingly complimentary foreword and compliments Clarke's short stories handsomely. Ignition is also really fun to read, it contains some great stories, and wicked phrases.

I learned most from the chapter on rocket performance and I now have a much better understanding of Specific Impulse. It's normally defined as the thrust of the rocket (in pounds) divided by the rate that the rocket consumes fuel (in pounds per second). It comes out in seconds. I've never been particularly happy that the quality of a rocket motor is measured in time, but I have manage to justify it to myself by thinking that it's sort-of how long a rocket could hover before it runs out of fuel. Clarke shows us that it's a ridiculous measure brought about by the horrific ambiguity of force and mass in American scientific units. If you just apply Newton's Laws, common sense, and basic algebra you can see that all the fuel being consumed is coming out the back of the rocket (or there's something badly wrong with your design) and that the force applied to your rocket is the same force that's accelerating you exhaust stream.

Specific impulse becomes the velocity of the exhaust of a rocket divided by the standard acceleration due to gravity. Clarke correctly points out building a rocket whose sole purpose is to get away from earth and then expressing its exhaust velocity in terms of the gravity of earth is "parochial and extremely silly". He prefers to think of Specific Impulse as a velocity expressed in units of 32 feet (or 9.8m) and while that works well it offends my dimensional analysis sensibilities. I now think of Specific Impulse as the length of time that a stone dropped in a vacuum takes to gain the same velocity as the exhaust stream.

The book is rather dated. It doesn't cover any developments past the late 60s and it amused me when he talked about Boron Nitrate and discussed the theoretical possibility and the early research that suggests it might have a hard cubic form analogous to diamond.

Richard "8 out of 10 would read again" B

Synchronicity

A couple of weekends ago I took my sports car to a track day at Donington Park (GP layout). It's a great track and we had a wonderful day. There was also a couple of very unlikely coincidences (or we're living in the matrix, there was a segmentation violation and my private memory area spilled out into the general simulation).

We were there on a Friday, but the paddock was already filling up with cars that would be racing at the weekend. One of the races was "Mighty Minis" and we had great fun peering at the race-prepared classic minis. One of my more disparaging comments was "I don't think much of their fusebox". A circuit board full of fuse holders was screwed straight onto the shelf above the passenger's knees (if there were a passenger seat) with no cover or protection of any kind. About a minute later when we had walked back to my car, the glue on the back of the velco that holds my luxuriously appointed fusebox cover in place failed. The fusebox cover fell clanging into the passenger footwell. "I don't think much of your fusebox" said my friend.

During that same short walk across the paddock I overheard one of the mini racers say "He'll be here tonight, he's getting a lift up with Paul Inch". I said to my friend that that was someone else coming up from Plymouth. "How do you know he's from Plymouth?" "Paul Inch is an engine builder in Plymouth" "That's just a man's name, I bet there's more than one. He could be from anywhere". The next mini we passed had the bonnet open and a "Paul Inch" sticker was clearly visible on the rocker cover with an 01752 (Plymouth) telephone number.

At the same time, 150 miles away, the postman was delivering a Hillman Imp fanzine to my friend and both the racing cars on the front cover had "Paul Inch" header strips on their windscreens.

Richard "coincidence or something more?" B

Happy Birthday

This year I have had a couple of delightful things drop through my letterbox. In the middle of April I got a birthday card from one of my friends. It was unexpected because my birthday is in July (his other friend called Richard, who's birthday is in April didn't get a card this year) and it really made me happy.

I've always been interested in rocketry. As a child I tried and failed to make my own rockets, but kept all my fingers. As soon as model rocket motors were available in the U.K. I was using them, and I managed to do the final year project of my computer-science/electronic-engineering degree in association with the space science laboratory.

Since about 1991 I have been trying to read a particular book about the development of rocket fuels. It's no longer in print and I have never seen a second hand copy for sale in real life. Since the rise of internet shopping I sometimes look for it, but it's too expensive. A tattered paperback is nearly £100 and a nice one or a hardback can be several hundred pounds.

Last week there was a pristine copy of this book on my doormat in an Amazon package. No receipt, no explanation, no clue who paid for it. As best as I can tell I haven't made an expensive mistake with "one-click-ordering" and I haven't got drunk and bought my sober-self a generous gift.

To my mysterious benefactor: Thank you very much, I'm delighted with the book, I have no idea how you can have known how much I wanted it.

If the valuable-and-hard-to-come-by-book-fairy reads my blog, let me say this: Milliken and Milliken "Race Car Vehicle Dynamics" ISBN 1560915269

Richard "Thank you" B